Alistair Darling’s finger-jabbing assault during the televised referendum debates with Alex Salmond (“What's your Plan B, Alex?”) infuriated many in the Yes camp.

Of course there is a plan B – and C and D. If only Mr Salmond would spell them out.

Scotland could have set up a nominal currency pegged to the pound, “sterlingisation”; or set up an independent currency like Norway’s; or joined the euro. The trouble was, none of these would have fared any better than the SNP’s policy of a continuing currency union.

Jim Sillars believes that the failure to go for an independence currency was wrong both ideologically and politically. It is hard to argue that Scotland could truly be independent if the Bank of England were deciding interest rates and the UK Treasury setting limits on Scottish borrowing.

More immediately, the problem with currency union was that Westminster wasn't buying it. “If you walk away from the UK you walk away from the pound,” said George Osborne. It was a little like planning a wedding ceremony when your prospective partner was leaving the country.

But it is naive to believe that, if the Yes campaign had gone for a separate currency, this would have made the case for independence any more persuasive. Mr Osborne would simply have said: “Do you really want Scotland to be isolated, at the mercy of financial markets, in a cruel sea without the security of the Bank of England as lender of last resort? Look at Iceland.”

A short-term financial crisis might very well have arisen if the Scottish Government had opted for immediate currency separation. With big UK companies disappearing over the Border and Scots putting their savings beyond reach, a period of currency instability would have been almost inevitable.

This was why the Nobel laureate economists on the Scottish Government’s fiscal commission in 2013 recommended a common currency, at least in the medium term.

Why put up border posts and force people to change currency every time they visit relatives in England? Why force companies to undergo transaction costs every time they export across the border? Above all, why submit to the hardship of amassing more than £100 billion in currency reserves to support a Scottish currency?

Even if the Scottish pound had been pegged to sterling on a one-to-one basis, the Scottish monetary authority or “currency board” would still have had to build reserves to back it up in case of a flight of funds; that is, unless the Bank of England agreed to back Scotland’s "pound”, which would be currency union by another name.

None of these is an insurmountable problem. But the least disruptive solution would surely be to retain currency union while the two countries disengaged economically. This would not perhaps be pure independence. But the Scottish Government was never proposing total separation.

Mr Salmond insisted that the 1603 Union of the Crowns should remain and that the Queen should be head of state. Many UK institutions would remain essentially unchanged, like the BBC and even possibly the armed forces (minus Trident).

The reality was that, in 2012, when the referendum was first announced, the Scots either lacked confidence that they could be an independent country or didn't feel it was worth the effort. Many changed their minds during the campaign, however, and the very rejection of currency union helped change them.

The image of a Tory chancellor erecting a financial Hadrian's Wall so that Scots couldn't use their own currency was highly damaging to the Union cause. The pound had never before been seen as “England’s property", something that could be taken away if Scots didn't behave.

Opinion polls during the campaign confirmed this. Support for independence rose after the Declaration, and by the eve of poll, according to Professor John Curtice, even a majority of No voters didn’t believe the Chancellor on currency union.

But looking back, the mere fact that currency was such an issue tells you something about the attitude of Scots to independence. Normally, when countries seek independence from foreign domination, currency is the last thing they think about.They want freedom.

Most Scots did not – and do not – feel oppressed by England, or denied liberty or civil rights. It's not like that here. But the diktat on the currency made many Scots reassess Scotland’s place in the UK, not as a colony but as a very, very junior partner; which is one reason the referendum result was so close, and why the SNP won a landslide in the subsequent General Election. It wasn’t the currency wot lost it.